I just now realized that Miko has access to exactly one form of healing.

[The Aboleth]

You're forgetting the much simpler Option 3: He's talking about end destination (the mountain) where he knows all the martyrs will go.

Oh, without a doubt. I guess my over-arching point was that there are a number of different ways you can read that conversation and still come to a conclusion that doesn't have Miko as DEFINITELY going to some other plane. Maybe she did, maybe she didn't--the only thing we know for sure is that she is not a Paladin anymore and never will be again, so whatever special perks Paladins might receive on the Celestial Realm--if she does still end up there--are things she will not be receiving because she lacks the requirements to receive them.